Waterless presensitized plate comprising four layers

ABSTRACT

A camera speed lithographic plate precursor composition is used for the preparation of waterless, imaged printing plates. The plates comprise a solid substrate with a first layer of a photopolymerizable, oleophilic coating; a second layer of silicone rubber; a third protective film layer; and a top or fourth layer comprising a silver halide emulsion containing polymeric binders or keying agents.

FIELD OF THE INVENTION

This invention relates to a camera speed, waterless lithographicprinting plate useful for the digitally controlled production ofprintable images using a single development process. Plate dampeningwith an aqueous fountain solution as conventionally employed in priorart lithographic printing operations is obviated by use of the waterlessprinting plate of the invention. The composition of the plate readilylends itself to the integration and implementation of digitized, andother, imaging devices for printable image formation on the plate.

BACKGROUND OF THE INVENTION

In conventional planographic printing, a printing plate bearing asoleophilic, ink receptive image is first dampened with an aqueousfountain solution to prevent ink from wetting the hydrophilic, non-imagebearing areas of the printing plate, after which an oil-based ink isrolled over the plate to selectively coat the now printable image.Conventional planographic printing has some difficulties inherent inhaving both an oleophilic ink and an aqueous fountain solution conjoinedin the same press. First, the fountain solution applied to the printingplate flows back into the train of inking rollers on the press, causingemulsification of the ink. Secondly, it is difficult to maintain controlof the delicate balance needed between the amount of ink and the amountof fountain solution applied to the printing plate. Consequently, theimage fidelity and uniformity are difficult to maintain. Thirdly, thefountain solution tends to flow forward over the offset cylinder,moistening the copy paper and thereby causing its dimensional change.Fourthly, in the case where printing is imaged directly byelectrophotography, the imaged printing plate must be subjected to anetching treatment and the printing operation becomes complicated.

Considerable effort has been applied in the industry directed toward thedevelopment of lithographic printing plates that may overcome some ofthe foregoing problems. A significant portion of that effort has beendirected toward the development of planographic plates that do not needa fountain solution circulating in the printing apparatus to accomplishthe printing function. These plates are referred to herein as waterlessplates or dry plates. For these waterless plates, the circulatingfountain solution is avoided by the discovery of various printingmethods and plate compositions that do not rely on the inducedhydrophilicity of a portion of the plate to distinguish an oleophilicimage surface from a non-oleophilic non-image surface.

U.S. Pat. No. 4,259,905 teaches a waterless, contact speed planographicprinting plate having an overlaying modified organopolysiloxanepolymeric material layer. The plate exhibits enhanced printing enduranceand produces prints of low background contamination.

U.S. Pat. No. 4,342,820 teaches a negative working waterless platerequiring no dampening water for use in negative work which comprises abase substrate, a light releasing photosensitive layer overlaying thebase substrate and the silicone rubber layer overlaying thephotosensitive layer. When the printing master plate is exposed througha negative film and then treated with a developer, only the siliconerubber layer overlaying the exposed photosensitive layer is removed,while the photosensitive layer remains as it is to form and image area.Dampening water is not required when printing is carried out.

U.S. Pat. No. 3,894,873 teaches a positive working waterless plate,comprises a base substrate, a light sensitive photoadhesive layeroverlaying a base substrate and the silicone rubber layer overlaying thephotoadhesive layer. When the printing master plate is exposed through apositive transparency and then treated with a developer, only thesilicone rubber layer overlaying the unexposed photoadhesive layer isremoved, while the photoadhesive layer remains as it is form an imagearea.

The waterless plates described in the foregoing patents are contactspeed and not for camera speed. The term "camera speed" indicates thatthe light-sensitive material in question is photographically sensitiveenough to permit imagewise exposure by focusing an original onto thelight-sensitive layer of the printing plate forming material through animage-focusing lens system or other high sensitivity or digitizedimaging devices. On the other hand, the term "contact speed" means thata light-sensitive material has a sensitivity such that it can be exposedthrough a negative or positive transparency placed in contact with it.Camera speed materials are photograpically sensitive to relatively lowenergy levels of light while relatively high light energy levels areneeded to expose contact speed materials.

Most light-sensitive lithographic printing plate materials presently incommercial use are of contact speed sensitivity. Thus an image-bearingtransparency of the original must be prepared before a printing platecan be made from a contact speed material. Consequently, the number ofsteps necessary to prepare the lithographic printing plates isconsiderably more than in the case in which no transparency isnecessary.

The sensitizers typically used in light-sensitive lithographic printingplate materials are diazo compounds, i.e., o-quinonediazide compounds,or light-sensitive polymers like polyvinyl cinnamates. However, thephotographic speed of these materials is too slow for the materialssensitized therewith to be of camera speed. Therein lies the reason forthe preceding statement to the effect that most light sensitivelithographic printing plate making materials are of contact speed.

The most common sensitizer used in photographic materials of cameraspeed is silver halide. Light-sensitive lithographic printing platematerials having solely a silver halide emulsion layer as theimage-forming layer have been produced. However, such plate materialsare comparatively difficult to process and the printing life thereof innot long. Other light-sensitive lithographic printing plate compositematerials of camera speed are known.

U.S. Pat. No. 3,567,445 teaches a presensitized lithographic printingplate with two different spectrally sensitive layers separated by aNovolak resin. The base layer is of the type used in a negative-workingpresensitized lithographic plate while the top layer is a silver halideemulsion layer.

U.S. Pat. No. 4,229,912 discloses a process for producing a lithographicprinting plate using a plate containing two light sensitive layers, oneof which is a gelatino-silver halide emulsion and the other is anon-silver halide layer. The patent teaches the use of a proteolyticenzyme to aid in the removal of the gelatino layer after imagewiseexposure followed by exposure of the non-silver halide layer.

U.S. Pat. No. 4,283,478 teaches a light-sensitive printing plate formingmaterial comprising a support having a hydrophilic surface provided witha layer of a positive-working light-sensitive resin composition capableof forming an oleophilic image, and a tannable light-sensitive silverhalide emulsion layer containing a tanning-developing agent.

U.S. Pat. No. 4,341,856 teaches printing plates containing at least twolight sensitive layers. Production of the final image-containingprinting plate requires at least two exposure steps.

U.S. Pat. No. 5,330,875, incorporated herein by reference, teaches aprocess for producing negative and positive original images on a bilevelprinting plate. The plate utilizes a contact speed (positive ornegative) layer and a camera speed (negative) overlayer in a singledevelopment process to form a temporary imagemask which is exposedsequentially to either the negative or positive original with theresultant image subsequently developable in a single process or step.

The objective of the present invention is to provide a camera speedwaterless lithographic printing plate wherein the need for conventionaldampening with an aqueous fountain solution in the printing operation isobviated.

A further objective of the invention relates to the presentation of awaterless lithographic printing plate amenable to the production ofpositive originals using digital imaging devices in a single developmentprocess.

Yet further objectives of the invention include the method for theproduction of the waterless plate as well as the methods for imageformation employing the waterless plate.

SUMMARY OF THE INVENTION

A camera speed lithographic printing plate precursor composition hasbeen discovered that can be used for the preparation of imaged printingplates that do not require the use of aqueous fountain solutions inprinting operations. The novel plates are effective in the reproductionof negative or positive images where the only liquids used in theprinting process are oleophilic inks. The full invention comprehends notonly the novel plate compositions but also the novel methods for theirproduction and image-wise utilization.

The invention generally relates to a light-sensitive combination ofmaterials for preparing a lithographic waterless printing plateprecursor comprising a light sensitive silver halide layer and a layerof a positive or negative working light-sensitive resin composition.More particularly, a camera speed, waterless lithographic printing plateprecursor has been discovered comprising a hydrophilic ornon-hydrophilic solid substrate with a first layer on the substratecomprising a photopolymerizable, oleophilic coating catalyticallyresponsive to direct actinic light exposure to produce an adhesivepolymer. Atop the first layer is an actinic light transparent secondlayer comprising a solvent swellable, ink repellant silicone rubber. Therubber coating is covered by a third layer comprising a transparent,protective film. Finally, the precursor contains a fourth layercomprising a gelatino silver halide emulsion. The fourth emulsion alsocontains polymeric binders or keying agents to promote adhesion of thefourth layer to protective film of the third layer. Thephotopolymerizable coating layer can be negative working or positiveworking.

For one embodiment of the invention the silver halide emulsion layer ortop layer is exposed to an actinic light having an intensity sufficientto expose the silver halide emulsion layer in order to form a latentimage. Preferably a digitized light source is used. The latent image isthen developed in a photographic developer and fixer to form a silverimage on the protective layer. The plate is then exposed to an actiniclight intensity sufficient to expose the photoadhesive layer. Theprotective film layer is removed and a developing liquid is applied tothe silicone rubber layer. The developing liquid causes unique swellingof the silicone rubber layer which has not been bound to thephotoadhesive layer in unexposed areas. Rubbing of the silicone rubberlayer with developing liquid removes the image areas of silicone rubberlayer that are not bound to photoadhesive layer. The effect provides anink-receptive surface in the image areas while the non-image areas ofthe silicone rubber layer bound to photoadhesive layer comprise an inkrepellent background area.

DETAILED DESCRIPTION OF THE INVENTION I. Composition of the WaterlessLithographic Plate

The lithographic printing plate precursor of the invention isconstructed of a substrate with four layers deposited on the substrate.

The Substrate Layer

The substrates which can be used in the instant invention are thosehaving the mechanical strength needed to withstand the rigors of theprinting process in which it is used. Solid substrates can bemanufactured from metal, wood, film, or composite material. Since theprinting process in which the plate is used is a waterless process, thesubstrate is not restricted to those having a hydrophilic surface asconventionally practiced. The substrate useful in the invention can haveeither a hydrophilic or hydrophobic surface as long as the surface canbe adapted to retain the first, presensitized coating layer. An aluminumsubstrate is preferred in view of its mechanical strength and thefamiliarity of that substrate to the printing industry.

The First or Photoadhesive/Photosensitive Layer

The first layer of the plate may be a positive-working photosensitivelayer or alternatively a negative-working photosensitive layer. Ineither case, the primary attributes of the negative or positive workingcoating of the first layer are sensitivity toward chemical conversionupon exposure to actinic light at contact speed and a capability to actas an adhesive bonding agent with the second silicone rubber layer.

i. Positive-Working Photosensitive Plate

The photoadhesive or photosensitive layer for a positive-workingpresensitized plate of the invention comprises an ethylenicallyunsaturated photopolymerizable monomer or oligomer having a boilingpoint above 100° C. derived from monoalcohols or monoamines having lessthan 30 carbon atoms or polyalcohols or polyamines having less than 80carbon atoms, a photoinitiator and, if necessary, an inhibitor of heatpolymerization, polymeric materials or an inorganic powder. Examples ofuseful coatings are listed in U.S. Pat. No. 3,894,873. The unsaturatedmonomers or oligomers are acrylates or methacrylates such asdimethylaminoethyl methacrylate, polyethylene glycol dimethacrylate,3-chloro-2-hydroxypropyl methacrylate, N,N,N',N'tertrakis-2-hydroxy-3-methacryloyloxy propylxylylenediamine,hydroxyacetoneacrylamide, or N-methoxymethylacrylamide.

Examples of photoinitiators include benzophenone, Michler's ketone,xanthone, benzoin, benzoin methyl ether, benzoin isopropyl ether,dibenzyl disulfide and uranyl nitrate.

Examples of polymeric materials include unsaturated polyester resinscomposed of units selected from ethylene oxide, propylene oxide,phthalic acid, bisphenol-A, maleic anhydride and fumaric acid, polyvinylacetate, polybutylmethacrylate, polyoctylmethacrylate, polyethyleneoxide, and soluble nylon copolymers.

In order to maintain photosensitivity of the presensitized plate andprolong the storable period very small amounts of heat polymerizationinhibitor are preferably added to the photoadhesive layer composition.Examples of such inhibitors are hydroquinone, phenothiazine,2,4-dinitrophenol and triphenylmethane.

If necessary, other additives may be included in the photoadhesive layerto make it solid enough to support the silicone rubber overlayerparallel with the base layer. The resulting plate shows a high scratchresistance and excellent storability.

ii. Negative-Working Photosensitive Plate

The alternative negative-working photosensitive presensitized plate ofthe invention comprises the quinonediazides usually employed forconventional positive working presensitized plates, wipe-on plates orphotoresist. These include the ester obtained frombenzoquinone-1,2-diazide sulfonates or naphthoquinone-1,2-diazidesulfonates and polyhydroxy compounds, e.g. benzoquinone-1,2-diazidesulfochloride with polyhydroxy phenyl, the ester fromnaphthoquinone-1,2-diazide sulfochloride and pyrogallol acetone resin,the ester from naphthoquinone-1,2-diazide sulfochloride andphenol-formaldehyde novolak resin; or complexes of diazonium compoundsand inorganic or organic acids, e.g., a photosensitive complex ofdiazodiphenylamine and phosphotungstic acid. The preferred componentsare selected from the group consisting of a reaction product of aquinonediazide with a polyfunctional compound, quinonediazideurethanized with a monoisocyanate, an esterified quinonediazide, anamidized quinonediazide, a quinonediazide graft polymerized with a vinylmonomer, so that the photosensitive layer is substantially insoluble ina developer.

The polyfunctional compounds employed as crosslinking agents arepolyisocyanate compounds, e.g., paraphenylene diisocyanate, 2,4 or2,6-toluene diisocyanate, 4,4'-diphenylmethane diisocynate,hexamethylene diisocyanate, isophorone diisocyanate, or adducts thereof,and polyepoxy compounds. e.g. polyethylene glycol diglycidyl ethers,polypropylene glycol diglycidyl ethers, bisphenol A diglycidyl ether,and trimethylolpropane triglycidyl ether. It is necessary that thecuring operation with these crosslinking agents be carried out underconditions under which the photosensitive substance will not lose itsphotosensitivity, usually at a temperature not higher than 126° C. Acatalyst may be added if necessary. The most preferred composition is acondensation product of quinonediazidenaphthoquinone-1,2-diazide-sulfonate with phenol-formaldehyde novolakresin. Examples of useful coatings are listed in U.S. Pat. No.4,342,820.

The negative photosensitive layer is capable of releasing the siliconerubber layer and constituting an image area in a selected area to be,exposed to the actinic light so that the silicone rubber layer can beremoved in the exposed image by a developer.

The Second or Silicone Rubber Layer

The silicone rubber layer of this invention comprises crosslinkeddiorganosiloxane obtained by curing silicone gums. Essentially, they areelastomers of high-molecular weight, about 400,000 to 800,000 formed bycrosslinked linear diorganopolysiloxanes, preferably dimethylsiloxane.Silicone rubbers suitable for use in the present invention are wellknown and are listed in U.S. Pat. Nos. 3,894,873 and 4,342,820.

The Third or Transparent Film Layer

The transparent film may be thinner than 10 mils (preferably thinnerthan 4 mils) to obtain good image fidelity. However, the film should becapable of providing an effective barrier to atmospheric oxygen in orderto protect the reactivity of the photosensitive first layer.Representative examples of such a transparent film include polyethylene,polypropylene, polyvinyl chloride, polyvinyl acetate, polyvinyl alcohol,polystyrene, polyethylene terephthalate, polycarbonate, cellulosetriacetate, polyester (Mylar by Dupont) etc.

In the present invention the preferred transparent films are polyolefinfilms such as polyethylene and polypropylene which have been treated toenhance their ability to adhesively bond with other films. However, anoverriding characteristic of the preferred films and any film used as athird layer is transparency to actinic light. To assure UV transparency,the films should contain a very minimum amount of conjugated olefinicunsaturated bonding, preferably non-conjugated olefinic unsaturation. Itis well known that UV absorbtivity is enhanced in a molecule to theextent that it contains conjugated olefinic unsaturation so that filmscontaining a significant amount of olefinic unsaturation would not besufficiently transparent to ultraviolet light for use in the presentinvention.

The Fourth or Silver Halide Layer

The top layer or coating of the lithographic plates precursor of theinvention comprises any type of gelatino silver halide emulsiondepending on the original to be produced, with the important exceptionthat it is distinguished over prior art emulsions in that it containsone or more special keying agents to facilitate adhesion between theemulsion layer and the third layer comprising the transparent film.Silver halide includes silver chloride, silver bromide, silver iodideand mixtures thereof as conventionally employed in the art. The averagesilver halide grain diameter is preferably between 0.01 and 5u.

In order to provide a suitable or desired sensitivity to the silverhalide, the grains thereof can be subject to chemical sensitization,e.g., sulfur sensitization, reduction sensitization, sensitization usingsalts of nobel metals such as Ir, Rh, Pt. etc., or spectralsensitization using sensitizing dyes. Silver halides of the latentsurface image type and inner latent image type can be used. The silverhalide emulsion generally contains various additives as known in theart. The gelatino silver halide light sensitive emulsion layer isprovided so that the dry weight is about 1 to 10 grams per square meter(g/m²), preferably from 3 to 8 g/m².

The silver halide layer of the invention also contains one or moreparticular keying agents or adhesion promoting agents which inducesilver halide emulsion to adhere to the thin transparent film layer. Thekeying agents includes water-borne latex emulsions in an amountconsisting of 10-35 weight percent, based on gelatin. The preferredamount is between 15-25 weight percent based on gelatin. The examples ofwater-borne latex includes polymethacrylamide, polyvinyl alcohol,acrylic acid polymers, polyamines, polyurethane and polyamides. Thepreferred polyacrylic acid latex emulsions are from polymethacrylic,polyacrylic and methylmethacrylate/methacrylic acid copolymers. Suchpolymers are described in the U.S. Pat. No. 4,283,478. In the presentinvention the most preferred water-borne latex for promoting adhesion onthe protective transparent film are from butyl acrylate/methylmethacrylate and vinyl acetate/butyl acrylate copolymers.

Ordinarily, silver halide emulsion would not adhere to the transparentfilm layer of this invention. A suitable silver halide emulsion layer ofthis invention requires good film forming properties and flexibility andremain adhered to the transparent film layer during storage andpreimaging operations. However, the keying agents, while promoting filmbonding, do not prevent removal of unexposed emulsion from the filmlayer by the developer after imagewise exposure of the silver halidelayer. Accordingly, the silver halide emulsion layer of this inventionis specially formulated to contain a keying agent or an adhesionpromoter which allows silver halide emulsion to adhere to the thintransparent film. The keying agents or adhesion promoters are selectedfrom group of polymers and copolymers of poly(methylmethacrylate/n-butylmethacrylate/methacrylic acid), poly(methylmethacrylate/methacrylicacid), poly(ethylmethacrylate), poly(isobutyl methacrylate),poly(methylmethacrylate) and poly(n-butyl/isobutyl acrylate) availablecommercially from DuPont, Wilmington, Del. under the trade nameElvacite; also selected from ethylene-vinyl acetate copolymer laticesavailable from National Starch and Chemical Co, N.J. under the tradename Duroset E-200 and latex emulsions of butyl acrylate/methylmethacrylate and vinyl acetate/butyl acrylate copolymers available fromUnion Carbide, N.J. under the trade name UCAR 441 and 447 water borneacrylic latex emulsions. Compounds listed as hardening agents in U.S.Pat. No. 4,283,478 may also be used in the present inventions. The mostpreferred are butyl acrylate/methyl methacrylate and vinyl acetate/butylacrylate copolymers which have glass transition temperature (Tg) in therange of 20°-30° C. These two most preferred latex emulsions providegood flexibility and film forming properties when mixed with the gelatinof the silver halide emulsion according to the method describe below.

The resin for keying agents such as poly(methylmethacrylate/n-butylmethacrylate/methacrylic acid) Elvacite 2016 available from DuPont isfirst pre-dissolved in an organic solvent selected from a group ofaliphatic ketones, preferably methyl ethyl ketone. It is then finelydispersed in a silver halide emulsion containing gelatin at 30°-40° C.with vigorous stirring or it is ball-milled in water with surfactant toform a water-borne latex emulsions. The water-borne latex emulsion canalso be prepared in the conventional method as known in the common art.In the present invention, preferred water borne latex emulsion forpromoting adhesion on the thin transparent film are from butylacrylate/methyl methacrylate and vinyl acetate/butyl acrylate copolymersat 10-35 weight percent based on gelatin, preferably between 15-25weight percent based on gelatin.

II. The Imaging Process

In the instant invention a digitally controlled laser is a preferredmethod for imagewise of the silver halide emulsion layer of the plate.It is known that photographic processes of making positive and negativefilm originals is time consuming and causes uncontrolled variations inthe process. Facilities and equipment adequate to support the processare required. To avoid these limitations, electronic alternativesadaptable to plateimaging have been developed that result in bettercontrol of platemaking, including digital direct platemaking systems andespecially systems coupled to laser imaging devices. For digitalplatemaking, the textual and graphics information stored in desk toppublishing or digital data storage systems can be modified on thecomputer before digitizing onto the plate. The high speed of textprinting from the resultant digitized plate provides considerableproductivity improvements over the conventional mode of platemaking.Hence, in the present invention digitally controlled image production ispreferred using a laser beam.

The method for image production on waterless lithographic printingplates using the photosensitive lithographic printing plate precursor ofthe present invention is depicted in the following steps:

First, the photosensitive layer containing silver halide emulsion isimagewise exposed to light at camera speed to form a latent image in thesilver halide layer. The silver halide layer is then treated with knowndeveloper and fixing solution to develop and fix the latent image. Thedeveloped images serve as a mask for the subsequent exposure step. Anexample of a developer and a fixer which can be used in the presentinvention is known in the art as disclosed in U.S. Pat. No. 4,229,912.

Following imagewise exposure and development, the plate is given anoverall exposure to actinic light of relatively high energy level, which.light impinges on the first, contact speed photosentive layer throughthe transparent intervening two layers of protective film and siliconerubber. For a positive worrying first layer, exposure results in thepolymerization of those parts of photosensitive layer corresponding tothe unmasked, non-image areas of the plate. The effect of thepolymerization is to form an adhesive polymer which bonds firmly to thesilicone rubber layer, but only in non-image areas. The photoadhesivelayer in the unexposed image area remains unpolymerized and does notbond to the silicone rubber layer.

Following the overall exposure of the plate to actinic light of contactspeed energy content, the protective film layer is physically removed topermit the treatment or development of the silicone rubber layer. Thatlayer is treated, preferably by soaking, with a developing liquid whichis capable of swelling the silicone rubber. Though the silicone rubberlayer of the plate is very thick, the portion of the silicone layer overthe unexposed part of the photosensitive layer that corresponds to theimage area is not adhesively bound to the photosensitive layer is easilyremoved, preferably by swabbing with cotton, to reveal a sharp,oleophilic image area of the photosensitive layer that underlies thepart of the silicone layer that was removed. The silicone rubber layerin the non-image areas remains bound to the photoadhesive underlayer andis not removed from the plate.

The developing liquids for positive working waterless plate are thosewhich can be absorbed by the cured silicone rubber and swell the saidlayer without affecting or weakening the bonding of the photosensitivelayer to the silicone rubber in the image area. The most usefuldeveloping liquids include isoparaffin or linear hydrocarbon, or amixture having those major components. These liquids are commerciallyand economically available from the fractional distillation products ofpetroleum. The fractions having lower boiling point are more absorbed bythe silicone rubber, which is more swollen and consequently can beremoved more easily then those treated by the fraction of higher boilingpoint. Thus gasoline is one of the most useful, convenient andeconomical developing liquids. These hydrocarbons do not usually affectand dissolve even the unhardened photoadhesive layer which remains onthe plate surface after the removal of the silicone rubber layer in theimage area.

Developing liquids for negative working waterless plate are those whichare capable of swelling silicone rubber. These are aliphatichydrocarbons (e.g. hexane, heptane, gasoline, kerosene), aromatichydrocarbons (e.g. toluene, xylene), or halogenated hydrocarbons (e.g.trichloroethane) and the following polar solvents: alcohols (e.g.methanol, ethanol), ethers (e.g. ethyl cellosolve, dioxane; ketones(e.g. acetone, methyl ethyl ketone; esters (e.g. ethyl acetate,cellosolve acetate).

III. The Printing Process

During printing operations the exposed surface of the oleophilicphotoadhesive layer corresponding to the image area accepts ink from theinking rollers. The silicone rubber background area that remains boundto the photosensitive layer is not wettable by oil-based inks.Therefore, ink is not removed from the rollers by the silicone rubberand they remain a non-printing part of the plate.

Since the resulting plate has a thick layer of silicone rubber which isfirmly bound to the photo polymerized underlayer in the non-imagedbackground area, this plate has high scratch resistance and is capableof printing more than one hundred thousand clean copies in the absenceof dampening.

Overall, the foregoing process uniquely allows the production ofprinting plates by the image-wise exposure of the plate precursors toobjects at camera speed while the plate precursor composition alsodirectly allows the production of a printing plate that is amenable towaterless printing operations.

IV. Waterless Lithographic Plate Production Process

The method of producing the plate of the invention is depicted asfollows:

A layer of photoadhesive composition is applied to a flexible substrateby a known coating apparatus such as reverse roll coater, blade coater,mayer bar knife, knife, etc. A silicone gum composition is applied overthe photoadhesive layer by coating a silicone solution or bytransferring a silicone film previously prepared over a releasablesubstrate. The silicone layer is cured to provide an elastic siliconerubber layer. When the silicone solution is coated over thephotoadhesive layer the solvents of the solution should not damage thephotoadhesive layer. A thin transparent protecting film is applied onthe silicone rubber surface by known lamination techniques. Theprotective film prevents the diffusion of atmospheric oxygen into thephotoadhesive layer. Finally, a silver halide emulsion layer is appliedover the transparent protective film by known coating apparatus.

The following Examples 1-3 (Negative Emulsion on Positive Plate) andExample 4 (Negative Emulsion on Negative Plate) are provided toillustrate various non-limiting embodiments of the present Invention:

Negative Emulsion on Positive Plate Example 1

A positive working waterless plate available from Toray Industries,Inc., Tokyo, Japan with the commercial designation "TAP" was overcoatedwith Polychrome's laser scanner negative silver halide emulsion (PC465)containing the adhesion promoter. The keying agent is available fromUnion Carbide as UCAR 441, an acrylic latex emulsion containing 45weight percent of butyl acrylate/methyl methacrylate copolymer. Thekeying agent was finely dispersed in a silver halide emulsion containinggelatin at 30°-40° C. with vigorous stirring. The weight of copolymer is15-25% based on gelatin. The plate is then dry by conventional method.The gelatino silver halide light sensitive emulsion layer has a dryweight of about four grams per square meter. The plate was digitallyexposed at 5 uJ/CM² on a Gerber Scientific blue argon-ion laser scanner(LE 55) with a negative original to form a latent image on the silverhalide emulsion layer. The plate was then processed in a rapid accessdeveloper (Polychrome PC126) and Polychrome fixer PF 200 to form asilver image on the protective film. The plate was then given an overallexposure of actinic (UV) light at 400 mj/cm² to expose the photoadhesivefirst layer. The protective film was then peeled off and the plate wasdeveloped with Toray's positive developer HP-7N and silicone rubber inthe unexposed areas removed by brushing. The unexposed areas of thephotosensitive layer comprise ink-receptive image areas, whereas theremaining silicone rubber layer comprise ink-repellent areas. The plateexhibits an excellent positive image from a negative original and can berun on a press to produce over 100,000 copies. By rolling up the plateson the press, the background becomes clean of ink while the image areasaccept ink. Following this procedure, the plate is ready for printing.

Example 2

A positive working waterless plate from Toray Industries, Tokyo, Japan,with the commercial designation "TAP" was overcoated with Polychrome'slaser scanner negative silver halide emulsion (PC465) containing theadhesion promoter (keying agent). The keying agent is available fromUnion Carbide as UCAR 447, an acrylic latex emulsion containing 60weight percent of vinyl acetate/butyl acetate copolymer. The keyingagent was finely dispersed in a silver halide emulsion containinggelatin at 30°-40° C. with vigorous stirring. The weight of copolymer is15-25% based on gelatin. The plate is then dry by conventional method.The gelatino silver halide light sensitive emulsion layer has a dryweight of about four grams per square meter. The plate was thendigitized and processes as in Example 1.

Example 3

A positive working waterless plate from Toray Industries, Tokyo, Japan,with the commercial designation "TAP" was overcoated with Polychrome'slaser scanner negative silver halide emulsion (PC465) containing theadhesion promoter (keying agent). The keying agent is available fromDuPont as Elvacite 2616 resin, an acrylic copolymer of methylmethacrylate/n-butyl methacrylate/methacrylic acid. It was dissolved inmethyl ethyl ketone at 8% and was then finely dispersed in a silverhalide emulsion containing gelatin at 30°-40° C. with vigorous stirring.The weight of copolymer is 15-25% based on gelatin. The plate is thendry by conventional method. The gelatino silver halide light sensitiveemulsion layer has a dry weight of about four grams per square meter.The plate was then digitized and processes as in Example 1.

Negative Emulsion on Negative Plate Example 4

Toray's waterless plate (TAN) was overcoated with Polychrome's laserscanner negative silver halide emulsion (PC-465) containing adhesionpromoter as in Example 1. The plate was exposed on Gerber Crescent 42plate setter using a positive original to form a latent image on thesilver halide emulsion layer. The plate was then processed in a rapidaccess developer (PC-126) and fixer PF 200 to form a silver image on theprotective film. The plate was then given an overall exposure of actiniclight at 500 mj/cm² to expose the photoadhesive first layer. Theprotective film was then peeled off and Toray's pretreatment solution(PTS-1) was applied to the plate to de-sensitize the plate and tostrengthen the link between the silicone rubber and photosensitive layerin unexposed areas. The silicone rubber in the exposed area is brushedoff. The photosensitive layer in the exposed areas provides anink-receptive image, whereas the remaining silicone rubber layer inunexposed areas provides an ink-repellent background area. By rolling upthe plate on the press, the background becomes clean of ink, whereas theimage areas accept ink; then the plate is ready for printing 100,000copies.

What is claimed is:
 1. A process for exposing a waterless presensitizedplate to an image, said process comprising:contacting said plate with acomputer controlled laser beam, said beam containing digitizedinformation corresponding to said image, wherein said plate comprises ahydrophilic or non-hydrophilic solid substrate; a first layer on saidsubstrate comprising an oleophilic photoadhesive coating containing anethylenically unsaturated photopolymerizable monomer or oligomer havingthe property of adhesively polymerizing when exposed to actinic light ora photoreleasable adhesive coating containing quinonediazides havingsolubilizable properties upon exposure to actinic light; an actiniclight transparent second layer comprising a solvent swellable, inkrepellant silicone rubber; a third layer comprising a polymericprotective film essentially transparent to actinic light; and a fourthlayer comprising a gelatino silver halide emulsion, said emulsioncontaining polymeric binders or keying agents to promote adhesion ofsaid fourth layer to said protective film.